Polycystic kidney disease (PKD) is a systemic nephropathy characterized by progressive bilateral renal cyst formation that results in a gradual decline in renal function. Although it is most commonly known as a kidney disease, the majority of patients with PKD die due to cardiovascular complications such as hypertension, aneurysm, hemorrhage, etc. Yet, not much attention is given to the basic science research on these complications, though the Office of Rare Diseases at the NIH recognizes PKD as an "orphan" genetic disease. At least in kidney epithelial cells, it has been shown that cilia function as mechanosensory organelles, and polycystins (PKD proteins), which are expressed to cilia, function as mechanical fluid sensory molecules. A recent study also shows that polycystins localize to the cilia of vascular endothelial cells. In particular, the roles of cilia in endothelia remain largely unknown, although one of the major sites of polycystin expression is in cardiovascular system, including in endothelial cilia. The present proposal is designed to study biophysical properties of endothelia in mechano-fluid sensing. We therefore propose to study how mechanosensory organelles, i.e. cilia, regulate the intracellular calcium-signaling pathway in vascular endothelia and how failure of these sensors leads to defects in vascular functions. Thus, this proposal addresses the main hypothesis that ENDOTHELIAL CILIA PLAY AN IMPORTANT ROLE IN THE MECHANICAL CAPACITY TO SENSE FLUID SHEAR STRESS. To evaluate the hypothesis, we will utilize aortic endothelial cells that lack ciliary function (Pkd1) and ciliary structure (Tg737) and have started to generate Pkd1 endothelial cell lines. The Tg737orpk mouse, which develops no cilia, also indicates vascular abnormalities. Specific aim 1 is thus designed to generate and characterize Tg737 endothelial cells; specific aim 2 is to identify the sensitivity of both Pkd1 and Tg737 cells to fluid shear stress. These aims are designated to understand the roles of cilia and polycystin ciliary molecules as 1) fluid-flow sensors, 2) regulators of calcium homeostasis, and 3) modulators of mechanical shear stress pathways. Together, the proposed studies will provide more detailed information on how mechanosensory cilia of endothelial cells can alter the cardiovascular system. These novel approaches to understanding blood disease falls within the scope of exploratory/development grant application to the NIH/NHLBI. [unreadable] [unreadable] [unreadable]